A cooperative, long-term, prospective study is in progress to study the effects of conventional drug therapy in patients with mild to moderately severe hypertension. At issue is the question of whether such treatment favorably influences the morbidity and mortality associated with the hypertensive state. An untreated group is compared with one treated with a combination of a thiazide diuretic and a rauwolfia serpentina preparation. Four hundred patients have been selected who are free of discernible cardiovascular renal complications. The incidence of these complications during follow-up is being monitored as specific end points.